1. 29 Aug, 2013 1 commit
    • Lai Jiangshan's avatar
      workqueue: fix possible stall on try_to_grab_pending() of a delayed work item · 31eafff4
      Lai Jiangshan authored
      commit 3aa62497 upstream.
      
      Currently, when try_to_grab_pending() grabs a delayed work item, it
      leaves its linked work items alone on the delayed_works.  The linked
      work items are always NO_COLOR and will cause future
      cwq_activate_first_delayed() increase cwq->nr_active incorrectly, and
      may cause the whole cwq to stall.  For example,
      
      state: cwq->max_active = 1, cwq->nr_active = 1
             one work in cwq->pool, many in cwq->delayed_works.
      
      step1: try_to_grab_pending() removes a work item from delayed_works
             but leaves its NO_COLOR linked work items on it.
      
      step2: Later on, cwq_activate_first_delayed() activates the linked
             work item increasing ->nr_active.
      
      step3: cwq->nr_active = 1, but all activated work items of the cwq are
             NO_COLOR.  When they finish, cwq->nr_active will not be
             decreased due to NO_COLOR, and no further work items will be
             activated from cwq->delayed_works. the cwq stalls.
      
      Fix it by ensuring the target work item is activated before stealing
      PENDING in try_to_grab_pending().  This ensures that all the linked
      work items are activated without incorrectly bumping cwq->nr_active.
      
      tj: Updated comment and description.
      Signed-off-by: default avatarLai Jiangshan <laijs@cn.fujitsu.com>
      Signed-off-by: default avatarTejun Heo <tj@kernel.org>
      [lizf: backported to 3.4: adjust context]
      Signed-off-by: default avatarLi Zefan <lizefan@huawei.com>
      Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
      31eafff4
  2. 20 Aug, 2013 34 commits
  3. 15 Aug, 2013 5 commits